CN111565626B - System for measuring mean arterial pressure - Google Patents
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- CN111565626B CN111565626B CN201880083231.XA CN201880083231A CN111565626B CN 111565626 B CN111565626 B CN 111565626B CN 201880083231 A CN201880083231 A CN 201880083231A CN 111565626 B CN111565626 B CN 111565626B
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- A61B5/021—Measuring pressure in heart or blood vessels
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- A61B5/14556—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases by fluorescence
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Abstract
The invention relates in particular to the field of anesthesia and to a method for real-time assessment of the mean arterial pressure of a patient by means of plethysmography measurements.
Description
Technical Field
The present invention relates to the field of anesthesia and more particularly to a new procedure and a new algorithm which can be used in particular for monitoring the general condition of a patient during anesthesia, in particular during anesthesia induction.
Background
The role of the anesthesia resuscitator is to observe and ensure control of the patient's primary vital functions during general anesthesia (throughout anesthesia, particularly during induction periods), which are critical periods of using large doses of anesthetic to induce loss of consciousness, often resulting in low arterial pressure.
This hypotension is caused by the interaction between the vasodilatory direct peripheral effects of hypnotic and morphine-like drugs and the central anesthetic effects of the arterial pressure control centers. In fact, arterial Pressure (PA) is a finely tuned physiological parameter that is compensated by a complex reflex system. During general anesthesia, all of these systems are subject to global inhibition corresponding to the depth of anesthesia. The risk associated with hypotension has been demonstrated, but the threshold at which perfusion consequences of one or more organs occur varies depending on the mechanism, the associated abnormalities (FC, cardiac output and oxygen delivery) and the specific region of the patient.
The main role of mean arterial pressure in the perfusion of organs, particularly those most susceptible to hypoperfusion (brain, heart, digestive tract and kidneys), is to expose these organs to the risk of failure when mean arterial pressure decreases.
In clinical practice, prevention of intra-operative arterial hypotension is widely practiced such that mean arterial pressure is maintained close to the initial mean arterial pressure before anesthesia, thereby reducing life risk and improving post-operative time. Furthermore, vasoactive agents (in particular phenylephrine, ephedrine and norepinephrine) are used during general anesthesia in order to correct any potentially harmful changes in mean arterial pressure as soon as possible.
Three arterial pressures can be measured in general: the cuff and stethoscope are used to measure systolic arterial pressure (pressions art e rielles systolique, PAS) and diastolic arterial pressure (pressions art e rielles diastolique, PDA), and the physician listens for the onset and disappearance of the pulse. These pressures represent the maximum systolic and minimum diastolic pressures, respectively, over the cardiac cycle. The mean arterial Pressure (PAM) representing the perfusion pressure of the organ was measured by a sphygmomanometer.
The sphygmomanometer (or electronic electrocardiograph manometer) does not use the principle of auscultation or palpation, but is an oscillometric method. The device records oscillations when the cuffs placed on the patient's forearm are automatically deflated. These oscillations start before the actual systolic value and end after the actual diastolic value. The maximum value of oscillation represents the mean arterial pressure (fig. 1). PAS and PAD are calculated from the PAM values and algorithms developed by the manufacturer. This is the device used by anesthesiologists in an operating room.
The mean arterial pressure can be estimated from the systolic arterial pressure and the diastolic arterial pressure by the formula pam=2/3pad+1/3 PAS. However, this formula is only one way of estimation discussed in the art, and other formulas have been studied (see, in particular, razminia et al Catheter Cardiovasc Interv, month 12 2004, 63 (4): 419-25). In the response given at RESEARCH GATE, gianni Losano (university of Duling) reviews the definition of mean arterial pressure (the average of all arterial pressure values throughout the cardiac cycle), and it may sometimes be the average of systolic and diastolic pressures.
https://www.researchgate.net/post/What_formulas_and_methods_exist_for_the_cal culation_of_mean_arterial_blood_pressure
Thus, knowledge of systolic and diastolic pressures appears to be insufficient to understand mean arterial pressure.
Accordingly, the goal of anesthesiologists is to protect the patient from surgical and anesthetic-induced physiological disturbances. In the case of long-term surgery, continuous monitoring of the cardiovascular system (heart rate, arterial pressure), the respiratory system (respiratory rate, pulse oximeter, carbon dioxide take-off) and the body temperature is required. Such control must be compatible with risks and circumstances to limit the onset of hemodynamic instability.
In particular, routine minimal monitoring includes measuring mean arterial pressure at least once every 5 minutes (invasive or non-invasive), and continuously measuring arterial oxygen saturation (SpO 2). These controls are required by the protocol.
Currently, non-invasive mean arterial pressure measurements are performed using oscillometric methods using cuffs as described above. However, one major limitation of such arterial pressure monitoring is that it is intermittent and therefore systematically lags behind the hemodynamic changes caused by anesthesia. Therefore, a continuous arterial pressure value cannot be obtained. In fact, arterial pressure measurements take about one minute and cannot be repeated too often to prevent repeated inflation of the cuff from injuring the patient's arm.
Pulse oximetry is measured by plethysmography using a sensor typically located at the fingertip. This measurement method is inexpensive and provides continuous information.
Such a sensor is called a pulse oximeter (volume pulse wave scanner) and comprises two red light emitting diodes which have to face the receiving area. The diode emits two lights (red and infrared) and the absorption of these lights by the pulsating flow is measured. This absorption of red and infrared light varies depending on whether it is encountered with reduced non-oxidized hemoglobin (Hb) or oxidized hemoglobin (HbO 2). Thus, the output data is absorption data. Fig. 2 shows that the absorption measured by the pulse oximeter contains several components, the only variable observed in steady state is systolic arterial flow.
Pulse waves are generated by each beat of the heart. It causes a change in the blood volume in the artery, which contracts and expands as it passes. This wave is heavily pulsed, reflecting (first peak) the expulsion of blood from the ventricle into the cardiovascular system (systolic pressure), and (second peak, or slope change of pulse wave decay after maximum), the residual propulsive force observed when the sigmoid colon valve closes, and representing relaxation (contraction) of the arteries near the heart, which dilate during blood advancement to absorb inflow of blood.
Recall that arterial pressure waves can be described in terms of their mean and pulsatile components. The average component is PAM, which is considered constant from the aorta to the larger peripheral arteries, while the pulsatile component varies according to the complex phenomena on the arterial tree.
Smart phone applications already exist as an aid to monitoring certain physiological parameters (Captesia, described in particular by Desebbe et al, ANESTH ANALG 2016; 123:105-13). Such applications require taking a photograph of the pulse wave pattern displayed by volume pulse wave tracing and sending the photograph to a server along with certain patient parameters. This application restores the pulse pressure variation but is not a real-time and continuous mean arterial pressure as it requires operator intervention. This application is relevant to patent application WO 2015/181622.
Application WO2017/037369 describes a non-invasive device for measuring the aortic flow of small mammals, which uses a device for volumetric pulse wave tracing of the chest by inductively measuring, acquiring and analyzing the varying signals of the cross section of each coil.
Application FR3024943 describes the process of determining the respiratory rate of an individual from the heart rate by measuring the heart signal by volume pulse wave spectrometry.
Application WO2007/128518 describes a non-invasive device for continuous measurement of Arterial Pressure (AP), characterized in that it comprises means for indirect measurement from a signal (VS) directly or indirectly representing a change in blood volume in an organ or site of the body, said volume change signal being calibrated using intermittent AP values obtained by standard non-invasive methods, preferably without using one or more predefined constants, in particular one or more physiological parameters assumed to be constant. The signal (VS) directly or indirectly representing the change in blood volume in an organ or part of the body may be a volume pulse wave of blood oxygen saturation (SpO 2) measured with an oxygen saturation meter on a finger, toe, ear, forehead, nostril or other organ or part of the body. The apparatus may comprise means for detecting the amplitude of the signal VS and the time at which the signal VS reaches its maximum value (VSmax) and/or its minimum value (VSmin) and/or a predefined reference Value (VSO) during each heartbeat (cycle) by calculating in real time:
Rise time (Tm) per heartbeat (cycle), defined as the time interval that the signal VS passes from value VSmin or value VSO to value Vsmax during the rise of the signal VS: tm=t (VSmax) -t (VSmin) or tm=t (VSmax) -t (VSO);
And/or a fall time (Td) of each heartbeat (cycle), defined as the time interval that the signal VS passes from value VSmax or value VSO to value VSmin during the fall of signal VS: tm=t (VSmin) -t (VSmax) or tm=t (VSmin) -t (VSO).
However, this document only describes the use of signal amplitude and peak rise time calibrated once per cuff to evaluate systolic arterial pressure. However, as previously described, this calibration is incorrect since the cuff only gives an estimate of the systolic blood pressure. Furthermore, this document does not disclose how to obtain the relation of the measured parameter on the pulse wave to the systolic pressure. Thus, the teaching of this document appears to be irrelevant to solving the problem presented in the present application (measuring mean arterial pressure, which is crucial for organ perfusion) since peripheral systolic pressure is not a good indicator of tissue perfusion. Furthermore, the systolic pressure depends to a large extent on the measurement location. Thus, it can be seen in fig. 1 that the contraction in plethysmography is not the same as the change in actual contraction. It should also be noted that the formula presented in this document uses a constant to take into account the diastolic pressure (the calculation is made at a pulsed pressure), which represents more or less the volume of blood pumped in and expelled by the heart. The use of this constant increases the uncertainty of the method in this document.
Patent US5269310 describes a method of determining arterial pressure by attaching a plethysmograph to a patient such that the plethysmograph interacts with an artery of the patient, the plethysmograph producing an output signal having a predetermined relationship to characteristics of blood in the artery; calibrating the plethysmograph during a calibration period by determining an actual arterial pressure of the patient using means other than the plethysmograph, then determining a value of a first arterial characteristic in a predetermined relationship between the first arterial characteristic, arterial volume indicated by the plethysmograph output signal, a converted value corresponding to arterial volume at infinite pressure, and the actual arterial pressure during the calibration period; and analyzing the plethysmograph output signal during a measurement period to determine an arterial pressure corresponding to the output signal according to the predetermined relationship. This teaches voltage measurements corresponding to systolic and diastolic (column 6) and voltage calculations corresponding to "average voltage". The method does not involve obtaining or using mean arterial pressure.
Patent US 5309316 describes a procedure for assessing arterial pressure based on two variables and essentially describes the use of pulse wave velocity and blood flow velocity.
Application US20070055163 describes the use of plethysmographic signals for measuring arterial pressure. The authors apply external pressure to the patient and measure the resulting signal so that the system is calibrated. However, this document does not mention that the dicrotic wave measurement can be used to measure or estimate mean arterial pressure.
Application US20110009754 relates to the calculation of arterial pressure and mentions the measurement of various parameters. Specifically, the measurement of the maximum value of the pulse wave or the time between the start of the pulse wave and the dicrotic wave is mentioned (fig. 7E). Thus, this document focuses more on the arrival time of the plethysmographic signal. This is clear in paragraph [0144], which indicates that "the speed of pressure pulsation through an artery is positively correlated with systolic blood pressure". Thus, as described above, the measurement of Pulse Arrival Time (PAT) and the index indicative of PAT may be used to estimate arterial blood pressure. Thus, although this document proposes a large number of parameters, it does not take into account measuring the height of the dicrotic wave nor does it suggest to pay attention to this.
Winokur et al (Conf Proc IEEE ENG MED Biol Soc.2012; 2012:2724-7) propose a device for monitoring Electrocardiography (ECG), ballistocardiogram (BCG) and angiogram (PPG) using two light sources. The document states that the Pulse Transit Time (PTT) extracted from the cross-correlation between PPG and BCG shows improved results compared to the pulse arrival time (PAT considered in US 20110009754) method of monitoring the mean arterial pressure variation.
Zachary Cohen (IEEE Sensors Journal, vol.17, no. 13, no. 7, 1, 2017) describes a prototype annular sensor for continuous measurement of blood pressure. This document describes a linear relationship between the measured voltage value per heartbeat in volts and the arterial pressure. This document describes the measurement of systolic and diastolic blood pressure.
Disclosure of Invention
The present invention relates to a new in vitro (ex vivo) method for continuously assessing in real time the mean arterial pressure of a patient, in particular a patient undergoing anesthesia, using values obtained in real time. Preferably, these values are obtained by plethysmography. Thus, this method allows the anesthesiologist to react immediately when a drop in blood pressure below a predetermined threshold occurs. It should be noted that the methods described below are not performed on the human body, but rather are performed in vitro using previous measurements. The present invention does not include measurement of these values, but only their operation (as described below) in order to obtain a reliable estimate of the arterial pressure of the patient.
Therefore, the method described below is preferably based on the measurement of the pulse wave resulting from contractility discharge by volume pulse wave spectrometry, and changes in mean arterial pressure, which, as described above, have no clear and direct relationship with systolic arterial pressure, can be inferred and monitored. The measurement by volume pulse wave spectrometry is performed using an oxygen saturation meter (pulse oximeter) on a finger, toe, ear, forehead, nostril or other organ or part of the body. Preferably, the measurement is made using a pulse oximeter on a finger or earlobe.
Since the relationship between the average pressure and the systolic and diastolic pressures is complex, and since the pulse wave represents the systolic pressure and is used to calculate the blood oxygen saturation, it is surprising that the pulse wave can be used to measure the average pressure of the whole. Such a result cannot be foreseen in view of the prior art and it can be noted that the above document does not mention this, although the average pressure is a meaningful parameter for confirming a good perfusion of the organ in anesthesia.
The present invention thus relates to a method (or process) for continuously assessing the mean arterial pressure of a patient based on continuously measured parameter values performed in vitro, comprising the steps of:
I. the calibration value Calib is calculated by:
a. Arterial pressure value at time t0
B. A value Vp0 obtained from the patient at time t0 that is related to the parameter measurement,
Estimate PAMest of arterial pressure of the patient at time t after t0 is calculated by the formula PAMest = k x Calib x Vpt, where Vpt is a parameter measurement obtained at time t.
Thus, the method provides an average arterial pressure value at each heartbeat. The method is very smoothly implemented by a computer and thus is performed in the computer.
Thus, the continuous mean arterial pressure can be estimated using the correlation coefficient Calib calculated based on the actual measurement value of the mean arterial pressure at the time t0 and the measurement value of the physiological parameter that can be continuously obtained at the same time t 0. The mean arterial pressure (at time t0 or later in the case of recalibration) is measured by any method known in the art (cuff or directly by intra-arterial probe). By measuring a new arterial pressure value and measuring a new parameter value Vp, the value Calib can be recalculated from time to time, in particular periodically, and then used until a new calibration.
Preferably, the continuously measured parameter Vp is measured by volume pulse wave spectrometry. Various methods of plethysmography exist and a preferred method in the context of the present invention is photoplethysmography.
This method allows to determine the excess blood volume per heartbeat (blood flow perfusion index, PI) associated with the blood evacuation after systole. PI is therefore expressed as a percentage of the "non-pulsatile" blood volume of the finger.
The method also measures the ratio of deoxyhemoglobin to oxyhemoglobin (referred to as SpO 2).
Photoplethysmography is presented by a graph representing the change in measured volume and the two values PI and SpO 2 described above. The graph represents pulse waves and reflects the blood evacuation at systole. It shows two pressure peaks (main peak at the outlet of the heart and second peak after relaxation of the blood vessels near the heart chamber (dicrotic wave)) that deliver blood into the body. Such a dicrotic wave may be graphically represented by a second peak, which appears as a high point during the decay of the observed main peak or as a change in slope during the decay of the main peak (corresponding to blood flow, where a new peak or high point cannot be formed when the blood flow is too low). At the level of the plethysmograph pattern, the shape of this second pressure wave (dicrotic wave) depends on several factors, such as the nature and accuracy of the plethysmograph, the state of the heart of the patient and/or the state of the blood vessels of the patient. However, as described above, this second pressure wave can always be detected.
In a preferred embodiment, the value of the dicrotic wave is used as the continuously measured parameter value Vpt. If a peak or high point can be observed, the height of the dicrotic wave is used (A in FIG. 4 and B in FIG. 4). If only a turning point in the decay curve is observed, the position of the turning point is used as the origin of the dicrotic wave (C in fig. 4). Very preferably, the height of the used dicrotic wave (dicrotic notch) preferentially adopts the total or absolute height of the volume pulse wave trace signal (Hd, fig. 3) compared to the height measured from the baseline of the pulsatile part (which corresponds to the diastolic height). In fact, the absorption rate of this baseline is likely to vary over time (B in fig. 7), which may lead to calculation errors if the absolute value of the absorption rate measured at the occurrence of a dicrotic wave is not considered.
In another embodiment, the value Vpt, which may be calculated continuously, is related to the logarithm of the inverse of the blood flow Perfusion Index (PI) at time t.
In another embodiment, the value Vpt used is the time from the start of the pulse wave to the dicrotic wave (the slope turning point observed when the pulse wave decreases), denoted as T2 in fig. 3.
In another embodiment, the value Vpt used is the time from the start of the pulse wave to the maximum of the pulse wave, denoted T1 in fig. 3.
In another embodiment, the value Vpt used is the period of the pulse wave (the time measured between the feet of two successive pulse waves), denoted T3 in fig. 3. When a plurality of variables are used, this parameter is used essentially as a secondary parameter, in particular for weighting PAMest calculated with another parameter.
In another embodiment, the value Vpt is the ratio of the value of the dicrotic wave to the value of the maximum systolic peak, or the value of the dicrotic wave to the value of the diastolic (foot of the pulse wave).
As described above, a pulse wave is a pressure wave that can be detected as a result of blood flowing to an organ, and thus is related to heart beat and heart contraction.
The use of the height of the dicrotic wave is very significant, which can be used to estimate the value of PAM. Advantageously, however, the blood flow perfusion index (directly, using its inverse or the logarithm of its inverse) may also be used. In fact, the blood flow perfusion index is inversely proportional to PAM (see example), i.e. as PAM decreases, the blood flow perfusion index increases. It can also be seen that the blood flow perfusion index is a very sensitive indicator that starts to "shift" (increase) as soon as PAM decreases, which is earlier than the change in the height of the dicrotic wave. Thus, it is conceivable to monitor both indicators (the height of the dicrotic wave and the blood flow perfusion index) simultaneously, if the blood flow perfusion index increases (or the inverse or log of the inverse decreases), care is required, and if the height of the dicrotic wave decreases after the blood flow perfusion index increases, care is taken. The invention therefore also relates to a method of (in vitro) assessing or estimating the mean arterial pressure of a patient, comprising the steps of:
measuring the value of the blood flow perfusion index, in particular by photoplethysmography
Evaluating the index or the variation of a function of the index (e.g. the reciprocal of the index, the logarithm of the reciprocal of the index)
When the blood flow perfusion index changes (increases) or the complex variable changes (reciprocal decrease of index, logarithmic decrease of reciprocal of index), the mean arterial pressure value is estimated by the following method (in particular by measuring the height of the dicrotic wave by photoplethysmography).
The invention also relates to a method (or process) for continuously assessing the mean arterial pressure of a patient based on continuously measured parameter values, comprising the steps of:
I. measuring mean arterial pressure of the patient at time t0
II, measuring parameter value Vp0 at time t0
Calculating a calibration value Calib by
A. Arterial pressure value obtained in step I at time t0
B. the value Vp0 of the instant t0 obtained in step II,
IV. measuring the parameter value Vpt at time t after t0
V. calculating an estimate PAMest of the arterial pressure of the patient at time t by the formula PAMest = k x Calib x Vpt, where Vpt is the measured value of the parameter obtained in step V.
Recalibration may also be performed from time to time (e.g. once every 5 minutes). The recalibration involves periodically recalculating the value Calib and using this new value Calib before the next recalibration.
The present application relates to an application for the treatment of a patient in need thereof, comprising the steps of: the vasopressor is administered to the patient when the estimated mean arterial pressure (PAMest) calculated by the method described herein decreases or falls below a predetermined threshold. This means that the patient is a hypotensive patient and that administration of a therapeutically effective dose of a vasopressor (which increases the reduced arterial pressure) will restore sufficient arterial pressure. Vasopressors are known in the art and include sympathomimetics (including epinephrine, dopamine, ephedrine), glucocorticoids and mineralocorticoids, and angiotensin amines, sympathomimetics are used in hospitals.
In a particular embodiment, the value Vpt used at time t is an average of a plurality of measurements over a predetermined time period. Any abnormal variation of the instant t can be avoided using such an average value. Specifically, an average of three systoles may be used.
In certain embodiments, the above method is performed on a patient during general anesthesia. Thus, the process lasts for several tens of minutes or even hours. It is recommended to recalibrate from time to time, especially in the case of arterial pressure readings taken from the cuff.
Thus, the above-described method (measurement of actual arterial pressure, measurement of parameters, calculation of the value Calib, and subsequent evaluation of arterial pressure using the value Calib) may be repeated several times at predetermined intervals. In particular, the method may be repeated each time the cuff pressure is read (i.e. the value Calib is substantially recalculated), or every two to three times. This avoids possible drift of the estimated mean arterial pressure value between two actual measurements. Calculation of the value Calib may also be performed if the estimated mean arterial pressure value differs too far (10% or 5% change) from the actual value measured from time to time.
In another embodiment, the value PAMest estimated at time t may also be refined by calculating several of these values (using different continuously measurable parameters) and differencing (estimating) the actual value PAMest based on the several results obtained. Thus, n individual measurements are made with n parameters (e.g., the time difference between the dicrotic waves, PI, peak-to-peak.) then PAMest are estimated for each parameter measurement and the final PAMest is calculated with probability.
Thus, an in vitro method for continuously assessing mean arterial pressure of a patient is described, characterized in that
A. The above method is repeated for different parameters to obtain a plurality of values PAMest at time t (each value associated with a particular parameter)
B. calculating a value PAMes by statistical estimation taking into account the following values
I. Different PAMest values calculated at time t
One or more PAMESTFINALE values calculated before time t.
Thus, in step a), PAMest may be calculated at time t based on measurements of parameters selected from the height of the pulse wave, the logarithm of the inverse of the blood flow Perfusion Index (PI), which is added 1 to avoid obtaining negative values, the duration from the start of the pulse wave to the counterpulsation wave, and the duration from the start of the pulse wave to the maximum of the pulse wave. Or a ratio (height of the dicrotic wave/maximum height of the pulse wave) and/or a ratio (height of the dicrotic wave/height of the diastolic part (foot of the pulse wave)) may be used.
Specifically, time t PAMest may be calculated based on the following combination of measured parameter values
Height of the dicrotic wave (reciprocal of the blood flow Perfusion Index (PI) +1) logarithm
Height of the dicrotic wave and duration of the dicrotic wave from the start of the pulse wave
Height of the dicrotic wave and time from the start of the pulse wave to the maximum of the pulse wave
-Height of the dicrotic wave, (logarithm of the blood flow Perfusion Index (PI) +1) and duration of the dicrotic wave from the start of the pulse wave
-Height of the dicrotic wave, (logarithm of the blood flow Perfusion Index (PI) +1), time from start of pulse wave to maximum of pulse wave
-The height of the pulse wave, the time from the start of the pulse wave to the maximum of the pulse wave and the time from the start of the pulse wave to the counterpulsation wave
-The height of the dicrotic wave, (reciprocal of the blood flow Perfusion Index (PI) +1), the duration from the start of the pulse wave to the dicrotic wave and the duration from the start of the pulse wave to the maximum of the pulse wave
Other combinations of altitudes that do not include a dicrotic wave are also contemplated and/or ratios (altitude of dicrotic wave/altitude of maximum pulse wave) and/or (altitude of dicrotic wave/altitude of diastolic portion) may be incorporated.
Preferably, the height of the dicrotic wave (or the ratio of the height of the dicrotic wave/the height of the systole ) is one of the variables to be measured and used, and the other variables are selected from the above variables. In fact, as shown in the example, the parameters related to the dicrotic wave (in particular the height of the dicrotic wave) give very good values of the mean arterial pressure and basically have the most important weights in the PAMESTFINALE determination, the other variables are basically used to weight the variables related to the dicrotic wave, which may be significant for some patients.
After step a) is performed, n estimates of mean arterial pressure are obtained (n being the number of selected parameters).
Step b) includes estimating the mean arterial pressure based on the n estimated values and the previously estimated values.
Such evaluation may be performed by any statistical method known in the art, in particular by using a Kalman filter in the discrete case. The Kalman filter in the discrete case is a recursive estimator. This means that only the estimated value of the previous state and the measured value of the time t are used for estimating the state of the time t. Thus, no history of observations and estimations is required.
The use of multiple parameter values and statistical probabilities, as well as filters (e.g., kalman filters), improves the reliability of the displayed measure of mean arterial pressure compared to measurements based on only a single parameter evaluation. In particular, this may be such that outliers obtained for the parameter at a given time (for whatever reason) are not too heavily weighted.
Thus, in another embodiment, an in vitro method for continuously assessing mean arterial pressure of a patient is described, characterized in that
A. The method described above is repeated for different parameters (Vpnt) in order to obtain a plurality of values PAMest at time t
(PAMestn) (each value is associated with a particular parameter)
B. the value PAMESTFINALE is calculated by combining the different PAMest values calculated at time t.
The combination described in step b) is preferably a linear regression and PAMESTFINALE is written as a1PAMest1+a PAMpest2+ &.. PAMestn corresponds to the PAMest value obtained for parameter Vpnt measured at time t.
The linear regression is performed by any method known in the art, wherein the relative weights of PAMestn values for each parameter are taken into account. The factors a1, a2 are preferably recalculated each time the average cuff pressure is actually measured.
Preferably, the quality of the coefficients can be refined using this method in case a certain amount of data is already available. For example, coefficients previously calculated in a contemporaneous group of other patients (at least 50, preferably at least 100 patients) may be used as initial coefficients. In fact, even if there is variability between patients and the coefficients obtained in the contemporaneous group are not necessarily the best for the patient under consideration, these previously calculated coefficients can be used before refinement from the data obtained for the patient. Thus, at each calibration
Using previously used coefficients (initial coefficients at the first calibration (from the contemporaneous group)
To calculate PAMest
-Comparing the value with the measured PAM value
-Adjusting the coefficients by increasing the weight of the patient's measured values in the regression when more PAM data measured for the patient is available.
Thus, the above method is based on the following: the mean arterial pressure may be measured from parameters that can be measured continuously, preferably by volume pulse wave tracing. Specifically, the height of the dicrotic wave (or the ratio to the total value of the contractile wave and/or the dicrotic wave) or the logarithm of the reciprocal of the blood flow perfusion index (plus 1) is proportional to the mean arterial pressure. Thus, the method for obtaining the mean arterial pressure is much simpler than the methods described in the prior art, while also being reliable.
As mentioned above, the method is particularly interesting for continuously monitoring the arterial pressure status of a patient while the patient is under general anesthesia. This allows the physician to take action quickly when the blood pressure is too low without waiting for actual cuff measurements.
Thus, these methods are preferably used continuously during general anesthesia throughout the patient.
In addition, to ensure patient safety, a signal may be sent when PAMest is below a predetermined threshold (which may be considered if the average arterial pressure is below 65 mmHg). Such signaling steps may be incorporated into the methods described above. The signal may be a graphical signal (e.g., the mean arterial pressure is represented in a color code different from a traditional color code (red instead of green or yellow when alerted)). Or the value may be displayed on the monitor in a different color code to alert the doctor to the risk of hypotension.
The warning signal may also (or alternatively) be an audible signal (long beep or otherwise) when the average arterial pressure falls below a predetermined value. This may also alert the surgeon to problems and the anesthesiologist needs to perform a medical procedure to correct the hypotensive problem.
The invention also relates to a computer product/program comprising program code instructions recorded on a computer readable medium for performing the steps of the above method when said program is executed on a computer.
The program may also include code instructions for displaying the mean arterial pressure value on the monitor. Code instructions may also be included to emit a visual and/or audible signal when the estimated mean arterial pressure value is below a predetermined threshold value (preprogrammed or entered by the clinician). Code instructions for making an actual arterial pressure measurement for the patient when the estimated value is below a predetermined value may also be included. Thus, the program can request and command arterial pressure measurements before a prescribed time without manual intervention.
The present invention also relates to a computer-readable recording medium having recorded thereon a computer program comprising program code instructions for executing the steps of the process as described above or the program as described above.
The invention may also include an apparatus for implementing a method as described above, comprising:
means for receiving mean arterial pressure measurement data, in particular data obtained by a non-invasive method (cuff)
Means for receiving measurement data of one or more continuously measured parameters, in particular of the height of the dicrotic wave or of the blood flow perfusion index
Calculation means of the coefficient Calib for each actual measurement of mean arterial pressure
Calculation means for calculating the mean arterial pressure at each instant t from the parameter values at instant t according to the method described above
Means for representing the mean arterial pressure calculated at each instant t (optionally comprising means for issuing an alarm in case the calculated mean arterial pressure is below a predetermined value)
-Optional means for automatically driving the means for measuring the mean arterial pressure in case the calculated mean arterial pressure is below a predetermined value
-Optional means for automatically administering a dose of vasopressor in case the calculated or estimated mean arterial pressure is below a predetermined value.
The computing device is essentially a processor capable of executing the computer product/program described above. The means for receiving data, the means for representing mean arterial pressure, the means for operating a sphygmomanometer or the means for automatically administering a dose of vasopressor is conventional in the art.
The above method is of great importance in the anesthesia field and in the post-operative care unit, but can also be used in other fields, such as resuscitation (especially in hyperventilation patients), cardiology, town medical or emergency medical (pre-and in-hospital). The methods and apparatus may also be used in sports medicine. These methods and devices may also be used to assess mean arterial pressure of a patient in a stress test.
The invention also relates to a method for analysing a plethysmographic signal and in particular to one or more methods for determining the foot of a pulse wave, the maximum value of a pulse wave and/or a dicrotic wave on a plethysmographic trajectory by applying the method described more precisely in the examples.
Specifically, the foot of the pulse wave is determined by calculating the second derivative of the volume pulse wave trace signal, the foot of the pulse wave corresponding to the maximum of this second derivative at the rising edge of the pulse wave. The first derivative may be weighted to focus only on the rising portion of the signal (i.e., when the first derivative is not positive, the second derivative is zero). Or the obtained values may be squared and then integrated over a floating window of a predetermined time, in particular a 240ms centered window (averaged over values 120ms before and 120ms after the desired point) in order to obtain a strong signal at each rising edge of the pulse wave. The signal may be compared to a threshold. Preferably, the threshold is adapted in real time. The threshold value may be calculated by the following formula: the integral is averaged over a 3s (centered or not centered) floating window (as calculated above) and its value is multiplied by 1.5. The peak (maximum) of the second derivative (which defines the foot of the wave) is determined in the region where the integral exceeds the threshold.
After finding the foot of the pulse wave, the peak value (maximum value) of the pulse wave can be determined by the following operations
Dividing the signal into several time windows (in particular windows between 20ms and 100ms, in particular windows of 50 ms), and
Looking at the maximum value in each time window (window by window can be advanced as long as a larger value is found in the time window of the last study).
The local maximum (corresponding to the maximum V found in the time window, which is smaller than the maximum in the next time window) corresponds to the maximum of the pulse wave.
This method makes it possible to obtain
Maximum (absorbance given by pulse oximeter corresponding to the peak of the contraction wave)
-The time to reach this maximum.
The value and time of the dicrotic wave can be determined by
-Obtaining the second derivative of the signal after the maximum of the pulse wave
Dividing the signal over a predetermined time window (between 50ms and 300ms, in particular 150 ms) after the pulse wave peak
Searching for local maxima of the second derivative of the signal in each time window in order to determine the region of interest (time window in which this local maximum of the second derivative of the signal is present)
-Searching for the absolute minimum of the first derivative of the signal in the region of interest. The search may be performed again, dividing the region of interest into time windows (between 5ms and 15ms, in particular 8 ms).
The point corresponding to the dicrotic wave corresponds to the point at which the absolute value of the first derivative is at a minimum. Its value (the absorption rate given by the pulse oximeter) and the time from the foot of the pulse wave to that point can then be measured.
Drawings
Fig. 1: examples of patterns of sphygmomanometer signals (obtained from https://www.infirmiers.com/etudiants-en-ifsi/cours/cours-cardiologie-la-pression-arteriel le-et-sa-mesure.html)
Fig. 2: pulse oximetry principle. (1): variable light absorption associated with arterial blood volume changes. (2) Constant light absorption associated with non-pulsatile portions of arterial blood. (3): constant light absorption associated with venous blood. (4): constant light absorption associated with tissue, bone, etc. According to Feissel, R animation 16 (2007) 124-131.
Fig. 3: representation of variables available in the context of the present invention based on pulse oximeter graphics. T1: the duration of the pulse wave from start to maximum; t2: the duration of the pulse wave from the start to the counterpulsation wave; t3: the total duration of the pulse wave; hd: height of the dicrotic wave.
Fig. 4: representation of different types of plethysmographic signals identified with a dicrotic wave.
Fig. 5: a flow chart illustrating a process according to the present invention is shown.
Fig. 6: a flow chart illustrating another embodiment of a process according to the present invention is shown.
Fig. 7: A. PAM (ARTm, long dashed line) representing a representative patient measured by invasive methods; PAM (PlethoMAP, short dashed line) estimated by the method according to the present invention based on the height of the dicrotic wave; PAM (NBPm, black dots) and calibration factors (Calib, solid lines) measured by cuff sphygmomanometer. B. Shows the time-dependent changes of the systolic peak (solid line), the dicrotic wave (short dashed line) and the diastolic wave (long dashed line) of the same patient at the same time. Also shown in this figure is a graphical representation of superimposed pulse waves, just to enhance the understanding of the three points (what each value corresponds to). Note that: the time scale of the pulse wave representation, which is typically lasting 1 second or less, is different from the time scale of the peak over time, which is only used for information providing purposes.
Fig. 8: a flow chart illustrating an embodiment of a plethysmograph signal analysis implementing the process according to the present invention is shown.
Fig. 9: dicpleth and PI. a=amplitude of a pulsation component (height of a contraction peak, pulsation portion) of the photoplethysmograph signal; b = height of dicrotic notch (pulsatile part); c = amplitude of the stationary component of the photoplethysmograph signal.
Fig. 10: median values of Δpam and Δdicapleth (a) and Δpam and Δpi (B) during anesthesia induction. Δ Dicpleth: dicpleth relative change from baseline; Δpi: relative change in blood flow perfusion index from baseline; Δpam: relative change of PAM from baseline. The graph shows changes in Δpam and Δ Dicpleth during 16 minutes of anesthesia induction. Starting from the start of induction (T0), every minute (T "x", the "x" minute starting from T0) represents the change in median PAM and Dicpleth from baseline.
Fig. 11: a flow chart illustrating the implementation of a procedure according to the present invention using measurements of the height of a dicrotic notch and the blood flow perfusion index is shown.
Detailed Description
The following examples illustrate various aspects and modes of practice of the invention. The embodiments described in the examples are part of the invention.
Example 1. Determination of parameters that may be used for continuous arterial pressure measurements
Therefore, in cardiology, the change in pulse wave can be measured noninvasively by volume pulse wave tracing. This produces a curve (graph) representing the excess volume resulting from the systolic ejection.
The blood flow Perfusion Index (PI) reflects the locally measured blood flow of the partially pulsatile arterial flow, i.e. systolic ejection volume. The blood perfusion index represents the area under the curve. In the case of photoplethysmography, a value SpO 2 representing arterial blood oxygen saturation is also obtained.
The curve represents the waveform of the pulse wave and shows the dicrotic wave at the outlet of the heart at the organ systole (second peak (optionally two peaks), high point or turning point in the decay).
Such a volume pulse wave trace signal may be used for continuous mean arterial pressure measurement.
Therefore, a change in the peak size (of the dicrotic wave), the area between two events (the value of the blood flow perfusion index), or a change in time in the waveform of the pulse wave is used. In particular, the attenuation of the dicrotic wave can be seen in practice, i.e. the dicrotic wave can be detected in the plethysmographic signal with certainty.
To determine these parameters, the pulse wave may be analyzed.
Foot of pulse wave
First, the foot of the pulse wave can be detected. The foot of the pulse wave is characterized by a rapid rise in the signal, resulting in a peak in the second derivative of the signal. By analyzing this second derivative of the signal obtained by the volume pulse wave scanner, a signal (peak of the second derivative) can be obtained at each rising edge of the pulse wave, thereby detecting the foot of the pulse wave and the moment corresponding to the start of the signal.
Contraction (pulse wave peak value)
For each cycle, the maximum value of the cycle is found from the foot of the wave. For this purpose, the signal can be divided into several time windows and a maximum value is found in each time window. In this way, a local maximum corresponding to the maximum of the pulse wave can be determined. The results are as follows
Maximum (absorption rate given by pulse oximeter corresponds to the peak of the systolic wave)
-Time to reach the maximum value
Therefore, the time from the start point of the pulse wave to the maximum value of the pulse wave can be calculated.
Dicrotic wave
Once the peak of the pulse wave is identified, the second derivative of the signal is analyzed over a predetermined time window (between 50ms and 300 ms). Local maxima of the second derivative after the systolic peak are found to determine the region of interest where the absolute minimum of the first derivative is found. The dicrotic point corresponding to the dicrotic wave corresponds to the point at which the absolute value of the first derivative is at a minimum. Its value (the absorption rate given by the pulse oximeter) and the time from the foot of the pulse wave to that point can then be measured.
Practical application example of the method
Signal acquisition
Signals are acquired in real time from a standard patient monitor that is capable of providing photoplethysmography waveforms and non-invasive arterial pressure by means of a pressure cuff. Typically via an RS232 serial port or an ethernet or WiFi network connection. In addition to these two basic parameters, a blood flow Perfusion Index (PI) value is used. The communication with the monitor may be bi-directional, e.g., allowing new non-invasive pressure gauge interfaces to be requested as needed.
Signal analysis
The signal processing is based on an on-line algorithm that measures the measured values and produces beat-to-beat results in real time.
Foot of pulse wave
The software uses a heartbeat detection algorithm that relies on the detection of the foot of the pulse wave. The foot of the pulse wave is characterized by a rapid rise in the signal, resulting in a peak in the second derivative of the signal.
The detection of the foot of the pulse wave is based on the second derivative of the signal. The second derivative is weighted by the first derivative to focus only on the rising portion of the signal (i.e., when the first derivative is not positive, the second derivative is zero). The obtained value is squared and then floating integrated over a centered window of 240ms (averaged over values 120ms before and 120ms after the desired point). This integrated signal provides a stronger signal at each rising edge of the pulse wave.
The signal is compared to a threshold. The threshold depends on the patient, the device used, the shape of the plethysmographic signal and the measurement noise. Since the measurement noise is not constant, the threshold must be adapted in real time. To calculate the threshold, use is made of the integral (calculated above), which applies a floating average with a 3s window (centered or not), the result being multiplied by 1.5. The threshold thus obtained may be used to define a region of interest where the integral exceeds the threshold. In this region of interest, the peak of the second derivative defines the foot of the wave.
Contraction (pulse wave peak value)
For each cycle, the detection of the dicrotic wave is completed in two steps, starting from the foot of the wave. The first step is to find the contraction and thus the maximum value of the period. For this purpose the signal is divided into windows of 50ms and as soon as a larger value is found the signal progresses gradually with the window. Once the maximum value is exceeded, a local maximum value (corresponding to the maximum or contraction value of the pulse wave) is found.
Dicrotic wave
Once the peak of the pulse wave is identified, the next step is to analyze the second derivative of the signal as it passes through a window of 150 ms. This finds the local maximum of the second derivative after the systolic peak. Once the peak is identified, the region of interest in which the dicrotic wave is located is known. From this point on, the first derivative is analyzed and the absolute minimum of the first derivative is searched for within a window of 8ms from the peak of the second derivative.
Thus the minimum of the first derivative of the peak near the second derivative is obtained. This point is defined as the dicrotic point corresponding to the dicrotic wave and its value (total absorption rate given by the pulse oximeter) can be measured.
Example 2 calibration and continuous estimation of mean arterial pressure (PAM/MAP)
Calibration requires at least one of the following parameter values (Vp)
Height of the dicrotic wave
Logarithmic (natural log or decimal log) value of reciprocal of PI blood perfusion index (ln (1/pi+1)). Adding 1 to the reciprocal of the blood perfusion index to avoid taking the logarithm of the value less than 1 to obtain a negative result
-Time value from foot of pulse wave to dicrotic wave, and
-Time value from foot of pulse wave to maximum value of pulse wave
The ratio "height of dicrotic wave/height of pulse wave" and/or "height of dicrotic wave/height of diastolic wave".
Duration of total pulse wave
These values can be obtained beat by beat (i.e. for each pulse wave). Fig. 3 shows how these variables are measured.
Calibration also requires an average arterial Pressure (PAM) value, which can be obtained, for example, by a non-invasive pressure cuff.
An average of the selected parameter values over a plurality of periods (2, 3, 4, 5, 6, 8 or 10 periods) may be used. This avoids disturbances such as respiratory pressure variations and irregular heart cycles. The average is preferably a statistical median rather than an arithmetic average.
In measuring the noninvasive arterial pressure, the calibration factor Calib is estimated, and is obtained by calib=pam/Vp. It is to be appreciated that the value Calib depends on the selected parameter, and that the value Calib obtained in the case where the dicrotic wave value is selected is different from the value Calib in the case where the logarithm of the inverse +1 of the blood flow Perfusion Index (PI) is selected.
Once the value Calib is obtained, the photoplethysmography signal is used as the sole data source to estimate the mean arterial pressure beat by beat.
Estimated PAM (PAMest) at time t is calculated by the following formula
PAMest = Calib x VPt, where Vpt is the selected parameter value (optionally average).
Application example (parameter is a counterpulsation wave)
Calibration requires beat-by-beat values of the dicrotic wave and intermittent values of mean arterial pressure, for example by a non-invasive pressure cuff. The dicrotic pressure values obtained by the dicrotic wave are averaged over several periods.
The number of cycles averaged is adjustable (e.g., 5 cycles). This prevents disturbances such as respiratory pressure variations and cardiac cycle irregularities. Averaging is done using statistical median rather than arithmetic average to be more robust in the presence of noise. In measuring non-invasive arterial pressure, the calibration factor is estimated and is based on the current average dicrotic value (Pdic) and the measured average arterial Pressure (PAM). Calibration factors were obtained by calib=pam/Pdic.
Continuous estimation of mean arterial pressure (PAM/MAP)
Once calibrated, the mean arterial pressure is estimated beat by beat using the absorbance measured by photoplethysmography as the sole signal source. Estimated PAM (PAMest) was calculated by PAMest =calib·pdic, where Pdic is the average of the dicrotic wave values as described above.
Another example (use of the blood perfusion index), in particular as signal quality
The PI value is used as an indicator of signal quality. In practice, PI values below 0.1% represent photoplethysmography signal differences and may indicate to the user that the estimation quality is poor and that more frequent calibration is required. In these cases, signal quality can generally be improved by correctly repositioning the sensor on the patient.
Incorporation estimation
PI gives information about the hemodynamic status in mean arterial pressure in the same way as a dicrotic wave and in a complementary way. In practice, PI generally develops in the opposite direction to the average arterial pressure.
A measurement called mPI (modified PI) was used and calculated as follows: mPI =10×ln (1/pi+1). The mPI thus obtained varies in the same direction as the mean arterial pressure and its behaviour is linearized with respect to the exponential behaviour of PI.
Calib is calibrated using the mean arterial pressure measured at time 0 and mPI, and the mean arterial pressure at time t is calculated using PAMest =calib×mpi (t).
Using a plurality of parameters
Several parameters (height, mPI, time of the above indicated dicrotic wave) may be used. Can be used for
Calib for periodic calculation of each parameter
-Calculating PAMest of each parameter
-Defining PAMest by statistical averaging (Kalman filter) by weighting these values PAMest and using the last calculated value.
Example 3 example in actual case
These results are based on the height of the dicrotic wave, and similar results can be obtained by other parameters.
Studies have been performed in neurosurgery or interventional neuroradiology procedures. The patient receives routine basic management of such interventions, including:
Monitoring
Non-invasive hemodynamic arterial pressure monitoring by oscillography and continuous ECG monitoring
Continuously monitoring arterial blood oxygen saturation (SpO 2) by photoplethysmography, and monitoring exhaled CO2.
-Bispectral index (bispectral, BIS) monitoring of depth of anaesthesia
Induction and maintenance of intravenous general anaesthesia (anesth si e rale selon une method intraveineuse a objectif de concentration (AIVOC)) with target concentrations including propofol and remifentanil, and arrowhead toxicity with atracurium besylate prior to tracheal intubation.
All monitors are connected to the philips monitor.
Hypotension is defined as a reduction of mean arterial Pressure (PAM) of at least 20% from basal PAM.
In the case of hypotension, the anesthesiologist in charge of the patient may self-relieve the anesthesia, administer a vascular filler or a vasoconstrictor (ephedrine 9mg, phenylephrine 50mcg or norepinephrine 10 mcg).
Experimental protocol
Stage 1: pre-dosing oxygen (baseline) -anesthesia induction.
Pre-oxygen supply 2 min: during this phase and prior to any injection, the base values (average of 2 values, baseline) for all parameters were recorded.
Remifentanil, target concentration of 5ng/mL, for 1 minute.
A target concentration of propofol, 5 μg/mL.
After BIS falls below 50, check if there is no ciliary reflection and manually supply oxygen to the patient: the arrowhead was poisoned with 0.5mg/kg of carpronin.
Manual oxygen supply, waiting 3 minutes.
Stage 2: laryngoscopy-intubation-manual ventilation.
Direct laryngoscopy.
Tracheal intubation.
Manual oxygen supply and probe attachment.
Stage 3: mechanical oxygen supply-anesthesia maintenance.
Connect the patient to the ventilator and begin mechanical ventilation.
The targets for remifentanil and propofol were reduced to 3.5ng/mL and 4. Mu.g/mL, respectively.
Continue harvesting for 3 minutes.
Stage 4: the possible hypotension is corrected by means of vasoconstrictors.
Treatment of the onset of hypotension with vasoconstrictors.
Collection was continued for 1 minute after the vasoconstrictor was validated.
End acquisition.
The cuff pressure was measured once per minute during the estimated average duration of 15 minutes at the beginning of phase 1, phase 2 and phase 3. If the anesthesiologist in charge of the patient thinks that a clinical situation is needed, he can deviate from the initial regimen himself at any time.
Data acquisition was performed using extended data acquisition software (Ixellence) to acquire signals and all values at a frequency of 125 Hz.
The acquisition points for all the following parameters were performed once per minute:
Height of the dicrotic wave: the height of the dicrotic wave is calculated from the volume pulse wave tracing signal.
-PI: the blood perfusion index was collected beat by beat.
Results:
61 patients were included in the study (median age 55 years, 32.7% male/67.3% female).
54 Of the 61 patients had at least one hypotension episode. Hypotension was defined as a >20% decrease in PAM, with a 88.5% probability of occurrence in the population. During induction, PAM <20% duration averages 5.2 minutes, i.e. 44% of the time.
Evolution of values throughout the induction period
The average duration of the whole induction phase was 12±4 minutes.
PAM variation and height of the dicrotic wave
During induction, the change in PAM and the change in the height of the dicrotic wave are highly correlated in a linear fashion (see fig. 7, in particular the stability of the value Calib (a in fig. 7)).
Analysis based on continuous mean arterial pressure measurement through invasive arterial cannulas
Arterial catheters are devices that allow access to an artery to invasively and continuously measure arterial pressure and take arterial blood samples.
Arterial pressure or invasive arterial pressure is an invasive technique for monitoring intravascular arterial pressure through an arterial catheter.
Continuous measurement of arterial pressure is carried out by means of an arterial catheter and by means of the method according to the invention (calculated using the height of the dicrotic wave measured by volume pulse wave tracing).
After the use of vasopressors, a good correlation between the PAM change measured through the arterial catheter and the above method was observed. The correlation was r=0.88, and the agreement between the variation obtained by this technique and the actual PAM measurement was 96% (a in fig. 7).
In a in fig. 7, a significant pressure change can be seen at the end, which is not detected by the cuff (due to the time between two pressure measurements), but by the PlethoMAP signal, thus emphasizing the richness of the information of the method using the dicrotic wave.
In B in fig. 7, it can be seen that PAM values are only obtained by measuring the height of the dicrotic wave, whereas the variation of the other two parameters (systolic or diastolic values) provides insufficient information. It can also be seen (t=1.15 h) that the drop in height of the dicrotic wave indicates an actual drop in PAM (a in fig. 7) without a change in systolic and diastolic pressures. Thus, the combination of these two pressures does not detect a drop in mean arterial pressure nor does it allow the anesthesiologist to take any corrective action.
Example 4 other parameters
Patients were studied according to applicable rules. Patients were over 18 years of age and received selective neuroradiological intervention after informed consent. The exclusion criteria for the study were arrhythmia (i.e., atrial fibrillation) and pregnancy.
Anesthesia protocol
Standard monitoring was initiated by an electrocardiogram, a noninvasive measurement device of the brachial artery ABP set to inflate every minute (philips france, france Lei Ne) and a digital pulse oximetry device placed on the second finger on the opposite side of the ABP cuff (philips france, france Lei Ne) prior to anesthesia induction. Bispectral index (BIS TM quatro sensor, miton force, france, bolonix, van. (Boulogne-Billancourt)) and neuromuscular block monitoring (TOF)ALSEVIA PHARMA, paris, france) is also used to monitor anesthesia. All monitoring parameters can be used on the Intellivue MP monitor of philips (philips, france, lei Ne). Anesthesia induction was performed with remifentanil and propofol at initial doses of 5ng/mL and 5 μg/mL, respectively, and adjusted so that BIS was between 40 and 60. Neuromuscular blockade was performed by intravenous injection of 0.5mg/kg of atracurium after BIS fell below 60 and was unconscious. The patient was then mechanically ventilated by direct laryngoscope endotracheal intubation (end-tidal = 6mL/kg ideal body weight, end-tidal positive pressure = 5cmH 2 O, respiratory rate and oxygen fraction to end-tidal CO 2＝4.7kPa,O2 saturation > 95%).
Arterial pressure was measured every minute during induction period and every 5 minutes after stabilization of the endotracheal tube. The patient's anesthesiologist can change the measurement frequency at any time and treat the IOH episode with fluid loading and/or vasopressors (phenylephrine and/or norepinephrine). After induction, some patients may also benefit from continuous, invasive arterial pressure monitoring.
Data acquisition
All parameters and monitoring curves displayed on the screen are recorded on the computer. Hemodynamic parameters (heart rate, arterial systolic pressure (SAP), mean Arterial Pressure (MAP) and diastolic pressure (DAP)) and PPG parameters (dichloropleth, PI and SpO 2) were then retrospectively acquired every minute during induction. Induction period was arbitrarily set from pre-oxygenation to 3 minutes after connection to mechanical oxygenation. The baseline value was obtained by averaging two measurements (one minute apart) prior to injection of anesthetic during pre-oxygenation. The "pre-boost" value is defined as a measurement of pre-vascular boost dosing during the onset of IOH. The "peak boost" value is defined as the maximum effect of vasopressor administration when the highest PAM is reached. Consistent with most studies, IOH is defined as a reduction of more than 20% from baseline PAM.
Dicpleth and PI measurements
Dicpleth is obtained a posteriori by the PPG waveform recorded by the operator who is unaware of the ABP value. Dicpleth is defined as the ratio of the height of the dicrotic notch (from the lowest point of the complex to the notch) to the height of the systolic peak (from the same lowest point of the complex to the image) measured at the end of the expiration time of a mechanically ventilated patient (average of 3 consecutive complexes) (fig. 9). PI (blood perfusion index) is provided by the manufacturer and calculated as the ratio of the pulse component to the DC component of the PPG signal (fig. 9).
During induction, Δmap, Δ Dicpleth, and Δpi were calculated as their relative percent change from their reference values. During vasopressor administration, the variation of the individual parameters is calculated as a measure from "pre-boost" to "peak boost".
DICRADIAL measurement
In patients with invasive blood pressure monitoring during anesthesia maintenance, DICRADIAL is also measured by arterial pressure signals using the same method as Dicpleth. DICRADIAL from the height of the dicrotic notch to the height of the contraction peak was calculated using the last 3 heartbeats at the end of the expiration time. In these patients, dicpleth, dicradial during the administration of the vasoconstrictors and their relative changes (Δ Dicpleth and Δ DICRADIAL) were also analyzed.
Statistical analysis
Values are expressed as median and quartile ranges (25% to 75%). The Wilcoxon grade test was used to analyze the parameter changes. During induction, the percent identity between Δmap, Δ Dicpleth, and Δpi was calculated. The lower curve area (aires sous la courbe, ASC) of the subject operating characteristic (ROC) curve (95% confidence interval) for Δ Dicpleth and Δpi for detecting IOH episodes was estimated and optionally compared using the dilong test. The Youden method is used to determine the optimal thresholds for Δ Dicpleth and Δpi for detecting IOH episodes. A ROC curve combining Δ Dicpleth and Δpi is constructed using a logic model. Correlation between the two was checked using the Spearman test. P <0.05 is considered statistically significant. The main objective of the study was to estimate the ASC of ROC curves of Δ Dicpleth and Δpi to track IOH during induction. The sample size was determined using an expected ASC of 0.85, an expected incidence of hypotension of 80%, and a confidence interval width of 1. With 80% of the power, then the number of patients involved is 62.16. A secondary objective is to estimate ASC (AUROC) of ROC curves combining Δ Dicpleth with Δpi. Using PrismStatistical analysis was performed (Graphpad software company, california, usa) and R3.3.0 (R base of statistical calculation, vienna australia). Dicpleth non-measurable patients at baseline prior to anesthesia induction were excluded from analysis.
Results
From 11 months 2014 to 5 months 2015, the study included 65 patients. Prior to anesthesia induction, dicpleth of 4 patients (6.2%) were not measured because no dicrotic notch was detected on the PPG signal (according to the class IV waveform of Dawber et al). Most patients are ASA II, with an average age of 54 years [39;64]. Hypertension, smoking and dyslipidemia are the most common complications. The reason for neuroradiological surgery is mainly due to aneurysms or arteriovenous malformations with procedural embolisms.
Changes in MAP, dicpleth and PI during Induction
The median time to induce anesthesia was 11[10;13.5] minutes. A total of 720 "hemodynamic data points" were recorded: 61 at baseline and 659 after anesthetic injection represent 659 changes from baseline.
MAP reference value 86[79;93 mmHg, the IOH limit of the individual is 69 < 62 >; 74 mmHg. PAM was lowered to 54[48 ] prior to laryngoscopy; after intubation of the trachea, PAM rises to 72 < 64 >; 82 mmHg. Average PAM over the induction period was 70[64;71 mmHg.54 patients (88%) had at least one IOH episode during anesthesia induction, representing 323 measurements (49% hemodynamic points). 28 patients (46%) received vasoconstrictor boosters (2 doses of phenylephrine and 26 doses of norepinephrine) during the induction period.
Dicpleth for baseline was 0.54[0.45;0.65] down to 0.36[0.19;0.45] (p < 0.001), and after intubation, rise to 0.46[0.41;0.56]. The PI value for baseline was 1.7[0.9;3] up to 4.4[2.8 ] before laryngoscopy; 6.6] (p < 0.001), lowering to 3.6[2.1 ] after endotracheal intubation; 5.4]. Fig. 10 depicts visual representations of Δmap, Δ Dicpleth, and Δpi during induction. The agreement between Δ Dicpleth and Δpam was 89% and the agreement between Δpi and Δpam was 90% (ESM 1).
Delta Dicpleth and DeltaPI for detecting the diagnostic manifestations of hypotension
Table 1 summarizes the diagnostic representation values for Δ Dicpleth and Δpi.
TABLE 1
Δ Dicpleth: dicpleth relative change from baseline; Δpi: relative change in blood flow perfusion index from baseline; ASC ROC: area under the subject's working curve; PPV: a positive predictive value; NPV: negative predictive value.
For IOH detection, the optimal cut-off values for Δ Dicpleth and ΔPI were-19% and 51%, respectively. ASCs of Δ Dicpleth and Δpi were not significantly different (p=0.22). Combining Δ Dicpleth with Δpi to detect onset of intrauterine homeostasis improves detection performance, ASC (0.91, (95% ci 0.88-0.95, p < 0.001) of ROC curve is statistically superior to Δ Dicpleth and Δpi alone (p=0.026 and p <0.001, respectively).
Changes in MAP, dicpleth and PI during vasoconstrictor administration
28 Patients (46%) received vasopressor dosing (2 doses of phenylephrine and 26 doses of norepinephrine) during induction. MAP from 59[50 ] after administration of vasopressors; 67 mmHg up to 76[68 ]; 79 mmHg (relative variation: 30% [14;45], p < 0.001). The number of people with diabetes is from 0.34[0.25;0.39 to 0.48[0.35;0.55 (relative variation: 44% [17 ], 63], p < 0.001), PI from 4.0[3.3;5.4] to 3.2[1.8;5.4] (relative variation: 28% [ -44; -13], p < 0.001). Δ Dicpleth and Δpi under the influence of vasopressors are closely related to Δmap (r= +0.73, 95% ci 0.48-0.87, p <0.001 and r= -0.62.95% ci-0.81 to-0.32, p <0.001, respectively).
Changes in the period Dicpleth and DICRADIAL of administration of vasoconstrictors
During the maintenance of anesthesia, 10 patients were given 48 norepinephrine doses (5 [4;6] per patient) under invasive arterial pressure monitoring. Excluded from analysis, dicpleth could not be measured at both hemodynamic points. MAP from 70[63;77 mmHg up to 88 < 77 >; 98 mmHg (relative change 26% [19;34], p < 0.001). Dicpleth from 0.28[0.17;0.36 to 0.39[0.25;0.46], DICRADIAL from 0.32[0.21;0.39 to 0.40[0.31;0.49] (relative changes are 34% [20;71], p <0.001 and 27% [14, 46], p <0.001, respectively). Dicpleth and DICRADIAL and their relative changes are highly correlated during the administration of vasoconstrictors (r=0.87.95% ci 0.83-0.90 and r=0.92.95% ci 0.85-0.95).
These results indicate that Dicpleth can be used as an alternative parameter for non-invasive and continuous MAP monitoring during anesthesia induction. These results indicate a strong correlation between Δ Dicpleth and Δmap under the action of vasoconstrictors. In IOH detection, dicpleth is reduced by 19%, the sensitivity is 79% and the specificity is 84%. PI represents the ratio between the pulse component and the continuous component of light absorption. The results show that there is a negative correlation between Δpi and Δmap under the action of vasopressors. Δpi is also accurate for IOH detection, but may not be as accurate as Δ Dicpleth in providing information about IOH intensity.
Claims (17)
1. A method of continuously assessing the mean arterial pressure of a patient based on a value Vp of a parameter continuously calculated by volume pulse wave spectrometry, comprising the steps of:
I. The calibration value Calib is calculated by the formula calib=pam/Vp 0, where PAM is the value of the mean arterial pressure measured at time t0, vp0 is the value measured for the patient at time t0 that is related to the parameter,
An estimate PAMest of the arterial pressure of the patient at a time t after t0 is calculated by the formula PAMest = Calib x Vpt, where Vpt is a measure of the parameter obtained at time t and the value of the parameter Vpt is the height of the dicrotic wave.
2. The method according to claim 1, characterized in that the value Vpt of the parameter is obtained from the finger or the earlobe by photoplethysmography.
3. The method according to claim 1 or 2, characterized in that the value of the blood flow perfusion index, the inverse of the blood flow perfusion index or the logarithm of the inverse +1 of the blood flow perfusion index is also calculated.
4. A method according to claim 1, characterized in that the value Vpt used is a value that averages a number of measured values over a predetermined period of time.
5. A method according to claim 1, characterized in that the value Calib is recalculated from time to time by measuring a new arterial pressure value and measuring a new value Vp of the parameter, and this new value Calib is subsequently used.
6. A method according to claim 1, characterized in that the value Calib is periodically recalculated by measuring a new arterial pressure value and measuring a new value Vp of the parameter and subsequently using this new value Calib.
7. A method for continuously assessing mean arterial pressure of a patient, characterized by
A. The method of one of claims 1 to 6 is repeated for different parameters to obtain a plurality of values PAMest at time t
B. The value PAMESTFINALE is calculated by statistical estimation taking into account the following values
I. Different PAMest values calculated at time t
One or more PAMESTFINALE values calculated prior to time t.
8. The method of claim 7, wherein the value PAMESTFINALE is calculated by Kalman filtering in the discrete case.
9. The method of claim 1 or 7, wherein the method is performed throughout the patient's general anesthesia.
10. An in vitro method of alerting a patient to a hypotensive state, comprising the steps of implementing a method according to one of claims 1 to 9, and signaling when the value PAMest is below a predetermined threshold.
11. The method of claim 10, wherein the signal is emitted by emitting a graphical signal or an acoustic signal, or a combination of these signals.
12. A computer readable recording medium having recorded thereon a computer program comprising program code instructions for executing the steps of the method according to one of claims 1 to 11.
13. Apparatus for performing the method according to one of claims 1 to 11, comprising:
means for receiving mean arterial pressure measurement data,
Means for receiving measurement data of one or more continuously measured parameters,
Calculation means for calculating the coefficient Calib of each actual measurement of mean arterial pressure,
Calculation means for calculating the mean arterial pressure at each instant t from the values of the parameters at instant t and the coefficients Calib,
-Means for representing the mean arterial pressure calculated at each instant t.
14. The apparatus of claim 13, the apparatus further comprising: means for issuing an alarm in case the calculated average arterial pressure is below a predetermined value.
15. The apparatus of claim 13, the apparatus further comprising: means for automatically driving the means for measuring the mean arterial pressure in case the calculated mean arterial pressure is below a predetermined value.
16. The apparatus of claim 13, the apparatus further comprising: means for automatically administering a dose of vasopressor in the event that the calculated mean arterial pressure is below a predetermined value.
17. The apparatus of claim 13, the parameter comprising a height of a dicrotic wave and/or a blood flow perfusion index.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
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| FR1762978A FR3075590A1 (en) | 2017-12-22 | 2017-12-22 | METHOD OF MEASURING AVERAGE ARTERIAL PRESSURE |
| FR1762978 | 2017-12-22 | ||
| FR1763405 | 2017-12-29 | ||
| FR1763405 | 2017-12-29 | ||
| PCT/EP2018/086748 WO2019122406A1 (en) | 2017-12-22 | 2018-12-21 | System for measuring the mean arterial pressure |
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| CN111565626A CN111565626A (en) | 2020-08-21 |
| CN111565626B true CN111565626B (en) | 2024-05-24 |
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| EP (1) | EP3727144A1 (en) |
| JP (1) | JP7285843B2 (en) |
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| US20220233079A1 (en) * | 2021-01-25 | 2022-07-28 | Samsung Electronics Co., Ltd. | Apparatus and method for estimating blood pressure |
| EP4223215A1 (en) | 2022-02-07 | 2023-08-09 | Assistance Publique Hôpitaux de Paris | Method and system for measuring pulse wave velocity |
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| JP7285843B2 (en) | 2023-06-02 |
| CN111565626A (en) | 2020-08-21 |
| WO2019122406A1 (en) | 2019-06-27 |
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| CA3086762A1 (en) | 2019-06-27 |
| EP3727144A1 (en) | 2020-10-28 |
| US11638529B2 (en) | 2023-05-02 |
| US20200390347A1 (en) | 2020-12-17 |
| AU2018391014A1 (en) | 2020-07-09 |
| AU2018391014B2 (en) | 2024-05-16 |
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